Systems, methods, and apparatus to permit communication between passive wireless transponders

ABSTRACT

Passive wireless transponders can perform transponder-to-transponder communication when illuminated by an interrogation carrier wave. The transponder-to-transponder communication permits each transponder to determine the identity of “other” proximately transponders. The transponder-to-transponder communication optionally permits each transponder to identify a “nearest neighbor” using one or more backscatter signal properties such as received signal strength or time-of-flight. Using this information and one or more externally supplied or internally stored instruction sets transponders can provide neighboring transponder data to an interrogator. Using this “neighbor” data, the interrogator can provide a system user with data indicative of the relative locations of a plurality of tags arranged in a one or two dimensional matrix.

BACKGROUND

1. Technical Field

The present disclosure generally relates to the field of passivewireless transponders, more specifically to communication betweenpassive wireless transponders in the presence of an externally appliedcarrier wave.

2. Description of the Related Art

Passive wireless transponders such as radio frequency identificationtags typically include an antenna, a control circuit or controller, anda limited quantity of nontransitory storage. Typically, each passivewireless transponder includes data indicative of a unique identifierhardwired or stored in the nontransitory storage (e.g., nonvolatilememory). Additionally, logic or machine executable instruction setsexecutable by the control circuit or controller may be optionallyhardwired or stored in the nontransitory storage. Passive wirelesstransponders receive energy when illuminated or interrogated by acarrier wave within a particular frequency range. When energized,passive wireless transducers may backscatter waves which may or may notcarry data. Additionally, the passive wireless transponders may executeone or more sets of machine executable instructions when energized. Suchmachine executable instructions permit passive wireless transponders toperform additional functions such as transmitting stored data, writingto nontransitory storage or interacting with the ambient environment.

Typically, a reader or interrogator transmits a carrier wave to energizethe passive wireless transponders. The reader and interrogator alsotypically receives backscatter signals from the energize passivewireless transponders. The reader may decode or interpret informationencoded or imposed on the backscatter signals. Sometimes one or morereaders or interrogators are communicably coupled to a host or backendprocessor-based system. The interrogator extracts the data carried bythe backscatter waves produced by each passive wireless device withinrange of the interrogator. Using the extracted data, the interrogator isable to perform various functions including information lookup (e.g.,determining the type and price of an item to which the passive wirelesstransponder is attached) and position determination (e.g., indicating anapproximate direction and distance to a particular passive wirelesstransponder).

BRIEF SUMMARY

Each of a plurality of grouped or otherwise accumulated passive wirelesstransponders can be configured to communicate with at least one otherpassive wireless transponder when exposed to an incoming radio frequencysignal such as an interrogation carrier wave. In some instances, one ormore signal parameters (e.g., signal strength, time-of-flight) of thebackscatter signals produced by each of the plurality of passivewireless transponders can be used to deduce the physical or spatialrelationship of one transducer to one or more other transducers. Forexample, the signal parameters of the backscatter signals may be used todeduce which transducers are positioned proximate a particulartransponder. Additionally, through the use of transponder-to-transpondercommunications achieved via backscatter waves, each transponder is ableto provide data indicative of other transponders that are positionedproximate the transponder providing the backscatter signal.

The ability to determine the relative physical relationship betweenpassive wireless transducers opens a new realm of possibilities for useof such transponders in commercial, security, and packagingapplications. In one example implementation, a number of frangible,passive, wireless transponders may be embedded or otherwise incorporatedinto a substrate such as paper or polymeric tape used to seal packagesfor shipment. In another example, the physical displacement of thepassive wireless transponders that occurs with removal or disruption ofthe substrate may result in an inability for the tags to communicatewith one another via backscatter waves. The frangible transponders arepositioned in the substrate at a distance permitting neighboringtransponders to “communicate” when illuminated by an interrogatorcarrier wave. In at least some instances, the interrogator carrier wavemay include one or more commands that are backscatter communicated byeach transponder to a neighboring transponder. In some instances, suchtransmission of the command between neighboring transponders occursuntil the originating transponder is reached to provide an indication ofsubstrate continuity. In other instances, such transmission of thecommand between neighboring transponders occurs until a defined endpointis reached (i.e., from a transponder positioned at the first end of thesubstrate to a transponder positioned at the second end of thesubstrate). Advantageously, once attached to a package or similarenclosure, any attempt to remove the substrate from the package willresult in the destruction of one or more frangible transponders.Destruction of a transponder will interrupt the backscattercommunication between neighboring tags, thereby providing an indicationof substrate discontinuity that may signal tampering with the packagehas occurred.

In another example, each item included in a collection of ordered items(e.g., library books, archive records) may include a passive wirelesstransponder. Data indicative of the identity of each transponder'sneighbor(s) is stored within a nontransitory storage coupled to eachrespective transponder. Upon receipt of an interrogation carrier wave,each transponder can backscatter communicate with neighboringtransponders to ascertain their identity. Improperly filed items,detected when transponders are unable to verify the identity of theirneighboring transponders, are advantageously located and data indicativeof the improperly positioned items communicated to a device such as anRFID interrogator.

In yet another example, each item in a two-dimensional matrix (e.g.,shoeboxes on a store shelf) may include a passive wireless transponder.Upon receipt of an interrogation carrier wave, each transponder canbackscatter communicate with neighboring transponders to ascertain theiridentity. The identity of each transponder, along with the identities ofneighboring transponders detected via backscatter communication istransmitted to an external device such as an RFID interrogator or abackend or host processor-based system. In at least some instances, theexternal device can compile a map showing the relative location of eachtransponder with respect to other transponders.

A method to determine the relative positions of a number of passivewireless transponders may be summarized as including receivinginformation from each of a plurality of passive wireless transponders,the information received from each of the passive wireless transpondersidentifying at least one neighboring passive wireless transponder thatis spatially proximate the respective passive wireless transponder fromwhich the information is received; and determining a relative positionof the passive wireless transponders with respect to one another basedat least in part on the information received from the passive wirelesstransponders.

Receiving information may include receiving information by aninterrogator system, and may further include providing an interrogationcarrier wave to the plurality of passive wireless transponders whichcauses at least some of the plurality of passive wireless devices tocommunicate with one another. Determining a relative position of thepassive wireless transponders with respect to one another based at leastin part on the information received from the passive wirelesstransponders may include determining the relative position of thepassive wireless transponders with respect to one another by a hostprocessor-based system, the host processor-based system remotely locatedwith respect to the interrogator system. Determining a relative positionof the passive wireless transponders with respect to one another basedat least in part on the information received from the passive wirelesstransponders may include determining the relative position of thepassive wireless transponders with respect to one another by theinterrogator system. Determining a relative position of the passivewireless transponders with respect to one another based at least in parton the information received from the passive wireless transponders mayinclude\ determining the relative position of the passive wirelesstransponders with respect to one another by at least one of the passivewireless transponders. Providing an interrogation carrier wave mayinclude providing by the interrogator system an interrogation carrierwave having a signal including data modulated thereon. Providing by theinterrogator system an interrogation carrier wave having a signalincluding data modulated thereon may include providing by theinterrogator system an interrogation carrier wave having a signalmodulated thereon, the signal including data representative of at leastone command.

The plurality of wireless transponders may be located about an enclosureand may further include determining based on the received informationwhether tampering with the enclosure has occurred; and causing anindication of tampering to be provided in response to a determinationthat tampering with the enclosure has occurred.

The plurality of wireless transponders may be located about packaging,and may further include determining based on the received informationwhether tampering with the packaging has occurred; and causing anindication of tampering to be provided in response to a determinationthat that tampering with the packaging has occurred.

The plurality of wireless transponders may be located across at leastone flap of a packaging and may further include determining based on thereceived information whether tampering with the packaging has occurred;and causing an indication of tampering to be provided in response to adetermination that that tampering with the packaging has occurred.

The method may further include determining if any of the passivewireless transponders are out of order with respect to in a definedarray. Determining a relative position of the passive wirelesstransponders with respect to one another based at least in part on theinformation received from the passive wireless transponders may includegenerating a virtual map of the plurality of passive wirelesstransponders, the virtual map which represents relative spatialpositions of the passive wireless transponders with respect to oneanother.

An interrogator system to determine the relative positions of aplurality of passive wireless transponders may be summarized asincluding a transceiver to provide an interrogation carrier wave; aprocessor communicably coupled to the transceiver; and aprocessor-readable nontransitory storage medium including machineexecutable instructions that when executed by the processor, cause theprocessor to: receive information from each of a plurality of passivewireless transponders that identifies at least one neighboring passivewireless transponder that is spatially proximate the respective passivewireless transponder from which the information is received; anddetermine a relative position of the passive wireless transponders withrespect to one another based at least in part on the informationreceived from the passive wireless transponders.

The machine executable instructions that cause the processor to receiveinformation from each of a plurality of passive wireless transpondersmay further cause the processor to: receive information from each of aplurality of passive wireless transponders located about an enclosure;determine based on the received information whether tampering with theenclosure has occurred; and responsive to a determination that tamperingwith the enclosure has occurred, generate a human perceptible outputindicative that tampering with the enclosure has occurred.

The machine executable instructions that cause the processor to receiveinformation from each of a plurality of passive wireless transpondersmay further cause the processor to: receive information from each of aplurality of passive wireless transponders located about an package;determine based on the received information whether tampering with thepackage has occurred; and responsive to a determination that tamperingwith the package has occurred, generate a human perceptible outputindicative that tampering with the package has occurred.

The machine executable instructions that cause the processor to receiveinformation from each of a plurality of passive wireless transpondersmay further cause the processor to: receive information from each of aplurality of passive wireless transponders located across at least onepackaging flap; determine based on the received information whethertampering with the package has occurred; and responsive to adetermination that tampering with the package has occurred, generate ahuman perceptible output indicative that tampering with the package hasoccurred.

The machine executable instructions may further cause the processor to:compare information received information from each of a plurality ofpassive wireless transponders with stored data indicative of a definedarray; and determine whether any of the passive wireless transpondersare out of order with respect to the defined array.

The machine executable instructions may further cause the processor to:generate a virtual map of the plurality of passive wirelesstransponders, the virtual map representative of the relative spatialpositions of the passive wireless transponders with respect to eachother.

A method of operation of a passive wireless transponder may besummarized as including in response to receipt of an interrogationcarrier wave, receiving information from each of a number of otherpassive wireless transponders by the passive wireless transponder; andtransmitting information identifying at least one of the other passivewireless transponders as a neighboring passive wireless transponder thatis spatially proximate the passive wireless transponder from which theinformation is received.

The method may further include categorizing at least one of the otherpassive wireless transponders as a neighboring passive wirelesstransponder. Categorizing at least one of the other passive wirelesstransponders as a neighboring passive wireless transponder may includecategorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder based at least in part on asignal strength of a signal received by the passive wireless transponderfrom one of the other passive wireless transponders. Categorizing atleast one of the other passive wireless transponders as a neighboringpassive wireless transponder may include categorizing at least one ofthe other passive wireless transponders as a neighboring passivewireless transponder based at least in part on a signal strength of asignal received by the passive wireless transponder from one of theother passive wireless transponders relative to a signal strength of asignal received by the passive wireless transponder from other ones ofthe other passive wireless transponders. Categorizing at least one ofthe other passive wireless transponders as a neighboring passivewireless transponder may include categorizing at least one of the otherpassive wireless transponders as a neighboring passive wirelesstransponder based at least in part on a time-of-flight of a signalreceived by the passive wireless transponder from one of the otherpassive wireless transponders. Categorizing at least one of the otherpassive wireless transponders as a neighboring passive wirelesstransponder may include categorizing at least one of the other passivewireless transponders as a neighboring passive wireless transponderbased at least in part on a time-of-flight of a signal received by thepassive wireless transponder from one of the other passive wirelesstransponders relative to a time-of-flight of a signal received by thepassive wireless transponder from other ones of the other passivewireless transponders. Transmitting information identifying at least oneof the other passive wireless transponders as a neighboring passivewireless transponder may include backscattering an interrogation carrierwave received from an interrogator system with the information encodedin the backscattered signal.

A passive wireless transponder may be summarized as including anantenna; a controller communicably coupled to the antenna; and anontransitory storage media communicably coupled to the controllerincluding machine-executable instructions that cause the controller to:receive information from each of a number of other passive wirelesstransponders responsive to the receipt of an interrogation carrier waveby the antenna; and transmit information that identifies at least one ofthe other passive wireless transponders as a spatially proximate,neighboring, passive wireless transponder.

The machine-executable instructions that may cause the controller totransmit information that identifies at least one of the other passivewireless transponders as a spatially proximate, neighboring, passivewireless transponder may further cause the controller to: identify atleast one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder based on a receivedsignal strength representative of a signal received from each of theother passive wireless transponders; and transmit information thatidentifies at least one of the other passive wireless transponders as aspatially proximate, neighboring, passive wireless transponder.

The machine-executable instructions that may cause the controller totransmit information that identifies at least one of the other passivewireless transponders as a spatially proximate, neighboring, passivewireless transponder may further cause the controller to: compare asignal strength representative of a signal received from one of theother passive wireless transponders with signal strengths of signalsreceived from other ones of the other passive wireless transponders;identify at least one of the other passive wireless transponders as aspatially proximate, neighboring, passive wireless transponder based onthe compared signal strengths; and transmit information that identifiesat least one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder.

The machine-executable instructions that may cause the controller totransmit information that identifies at least one of the other passivewireless transponders as a spatially proximate, neighboring, passivewireless transponder may further cause the controller to: identify atleast one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder based on atime-of-flight parameter of a signal received from each of the otherpassive wireless transponders; and transmit information that identifiesat least one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder.

The machine-executable instructions that may cause the controller totransmit information that identifies at least one of the other passivewireless transponders as a spatially proximate, neighboring, passivewireless transponder may further cause the controller to: compare atime-of-flight parameter of a signal received from one of the otherpassive wireless transponders with time-of-flight parameters of signalsreceived from other ones of the other passive wireless transponders;identify at least one of the other passive wireless transponders as aspatially proximate, neighboring, passive wireless transponder based onthe compared times-of-flight; and transmit information that identifiesat least one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder.

A method of operation may be summarized as including providing aninterrogation carrier wave to the plurality of passive wirelesstransponders, the interrogation carrier wave which causes the passivewireless transponders to transmit to a neighboring passive wirelesstransponder in a defined order; receiving information from at least oneof the plurality of passive wireless transponders, the informationreceived from the at least one of the plurality of passive wirelesstransponders indicative of whether each of the passive wirelesstransponders have successfully transmitted to a respective neighboringpassive wireless transponder in the defined order; and determining basedon the received information whether each of the passive wirelesstransponders have successfully transmitted to a respective neighboringpassive wireless transponder in the defined order. Providing aninterrogation carrier wave to the plurality of passive wirelesstransponders may include providing an interrogation carrier wave whichcauses the passive wireless transponders to successively pass a commandalong a defined sequence of the passive wireless transponders. Providingan interrogation carrier wave to the plurality of passive wirelesstransponders may include providing an interrogation carrier wave whichcauses the passive wireless transponders to successively pass a commandalong a defined sequence of the passive wireless transponders in aclosed loop starting from and ending with a first one of the passivewireless transponders. Providing an interrogation carrier wave to theplurality of passive wireless transponders may include providing aninterrogation carrier wave which causes the passive wirelesstransponders to successively pass a command along a defined sequence ofthe passive wireless transponders in a first direction from a first oneto a last one of the passive wireless transponders in the definedsequence. Providing an interrogation carrier wave to the plurality ofpassive wireless transponders may include providing an interrogationcarrier wave signal which causes the passive wireless transponders tosuccessively pass a command along a defined sequence of the passivewireless transponders in a first direction from a first one to a lastone of the passive wireless transponders in a first defined sequence andthen in a second direction from the last one to the first one of thepassive wireless transponders in a second defined sequence. Providing aninterrogation carrier wave to the plurality of passive wirelesstransponders may includes providing an interrogation carrier wave whichcauses the passive wireless transponders to successively passinformation along a defined sequence of the passive wirelesstransponders. Providing an interrogation carrier wave to the pluralityof passive wireless transponders may include providing an interrogationcarrier wave which causes the passive wireless transponders tosuccessively pass information along a defined sequence of the passivewireless transponders in a closed loop starting from and ending with afirst one of the passive transponders. Providing an interrogationcarrier wave to the plurality of passive wireless transponders mayinclude providing an interrogation carrier wave which causes the passivewireless transponders to successively pass information along a definedsequence of the passive wireless transponders in a first direction froma first one to a last one of the passive wireless transponders in thedefined sequence. Providing an interrogation carrier wave to theplurality of passive wireless transponders may include providing aninterrogation carrier wave which causes the passive wirelesstransponders to successively pass information along a defined sequenceof the passive wireless transponders in a first direction from a firstone to a last one of the passive wireless transponders in a firstdefined sequence and then in a second direction from the last one to thefirst one of the passive wireless transponders in a second definedsequence. The interrogation carrier wave may causes the passive wirelesstransponders to each retrieve from a memory of the passive wirelesstransponder a unique identifier for at least one respective neighboringpassive wireless transponder.

The plurality of wireless transponders may be located about an enclosureand may further include determining based on the received informationwhether tampering with the enclosure has occurred; and causing anindication of tampering to be provided in response to a determinationthat tampering with the enclosure has occurred.

The plurality of wireless transponders may be located about packagingand may further include determining based on the received informationwhether tampering with the packaging has occurred; and causing anindication of tampering to be provided in response to a determinationthat tampering with the packaging has occurred.

The plurality of wireless transponders may be located across at leastone flap of a packaging and may further include determining based on thereceived information whether tampering with the packaging has occurred;and causing an indication of tampering to be provided in response to adetermination that tampering with the packaging has occurred.

An interrogator system to determine the relative positions of aplurality of passive wireless transponders may be summarized asincluding a transceiver to provide an interrogation carrier wave; aprocessor communicably coupled to the transceiver; and aprocessor-readable nontransitory storage medium including machineexecutable instructions that when executed by the processor, cause theprocessor to: transmit an interrogation carrier wave to each of aplurality of passive wireless transponders that causes each of theplurality of wireless transponders to transmit a backscatter signal to aneighboring passive wireless transponder in a defined order; receiveinformation from at least one of the plurality of passive wirelesstransponders, the information received from the at least one of theplurality of passive wireless transponders indicative of whether each ofthe passive wireless transponders have successfully transmitted to arespective neighboring passive wireless transponder in the definedorder; and determine based on the received information whether each ofthe passive wireless transponders have successfully transmitted to arespective neighboring passive wireless transponder in the definedorder.

The machine-executable instructions that may cause the processor totransmit an interrogation carrier wave to each of a plurality of passivewireless transponders may further cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto successively transmit a command using a backscatter signal to adefined sequence of passive wireless transponders.

The machine-executable instructions that may cause the processor totransmit an interrogation carrier wave to each of a plurality of passivewireless transponders may further cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto successively transmit a command using a backscatter signal to adefined sequence of passive wireless transponders in a closed loop,starting and ending with a first one of the passive wirelesstransponders.

The machine-executable instructions that may cause the processor totransmit an interrogation carrier wave to each of a plurality of passivewireless transponders may further cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto successively transmit a command using a backscatter signal to adefined sequence of passive wireless transponders in a first directionfrom a first one to a last one of the passive wireless transponders in adefined sequence.

The machine-executable instructions that may cause the processor totransmit an interrogation carrier wave to each of a plurality of passivewireless transponders may further cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto successively transmit a command using a backscatter signal to adefined sequence of passive wireless transponders in a first directionfrom a first one to a last one of the passive wireless transponders in afirst defined sequence and then in a second direction from the last oneto the first one of the passive wireless transponders in a seconddefined sequence.

The machine executable instructions that may cause the processor toreceive information from each of a plurality of passive wirelesstransponders further cause the processor to: receive information fromeach of a plurality of passive wireless transponders located about anenclosure; determine based on the received information whether tamperingwith the enclosure has occurred; and responsive to a determination thattampering with the enclosure has occurred, generate a human perceptibleoutput indicative that tampering with the enclosure has occurred.

The machine executable instructions that may cause the processor toreceive information from each of a plurality of passive wirelesstransponders further cause the processor to: receive information fromeach of a plurality of passive wireless transponders located across atleast one packaging flap; determine based on the received informationwhether tampering with the package has occurred; and responsive to adetermination that tampering with the package has occurred, generate ahuman perceptible output indicative that tampering with the package hasoccurred.

A method of operation of a first passive wireless transponder may besummarized as including receiving an interrogation carrier wave by thefirst passive wireless transponder; in response to receipt of theinterrogation carrier wave, transmitting a first signal by the firstpassive wireless transponder to at least one neighboring passivewireless transponder; and receiving a second signal from at least oneneighboring passive wireless transponder by the first passive wirelesstransponder, the received second signal indicative of whether each of aplurality of passive wireless transponders, which includes at least thefirst and at least the neighboring passive wireless transponders, havesuccessfully transmitted to one another in a defined order.

The method may further include determining whether each of the passivewireless transponders have successfully transmitted to a respectiveneighboring passive wireless transponder in the defined order based onthe received second signal.

The method may further include determining by at least one circuit ofthe first passive wireless transponder whether each of the passivewireless transponders have successfully transmitted to a respectiveneighboring passive wireless transponder in the defined order based atleast in part on the received second signal.

The method may further include transmitting information to aninterrogation system by the first passive wireless transponder, theinformation indicative of whether each of the plurality of passivewireless transponders have successfully transmitted to one another in adefined order. Transmitting a first signal by the first passive wirelesstransponder may include transmitting a first signal which includes atleast one unique identifier that uniquely identifies a respectiveneighboring passive wireless transponder. Transmitting a first signal bythe first passive wireless transponder may include transmitting a firstsignal which omits any unique identifiers that uniquely identify anyneighboring passive wireless transponders. Transmitting a first signalby the first passive wireless transponder may include transmitting afirst signal which includes a unique identifier that uniquely identifiesthe first passive wireless transponder.

A passive wireless transponder may be summarized as including anantenna; a controller communicably coupled to the antenna; and anontransitory storage media communicably coupled to the controllerincluding machine-executable instructions that cause the controller to:transmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna; and receive a second signal from at least one neighboringpassive wireless transponder, the received second signal indicative ofwhether each of a plurality of passive wireless transponders havesuccessfully transmitted a defined signal to one another in a definedorder.

The machine-executable instructions may further cause the controller to:determine whether each of the passive wireless transponders havesuccessfully transmitted to a respective neighboring passive wirelesstransponder in the defined order based on the received second signal.

The machine-executable instructions may further cause the controller to:transmit a signal to an interrogation system, the signal includingindicative of whether each of the plurality of passive wirelesstransponders have successfully transmitted to one another in a definedorder.

The machine-executable instructions that may cause the controller totransmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna may further cause the controller to: transmit a first signalwhich includes at least one unique identifier that uniquely identifies arespective neighboring passive wireless transponder.

The machine-executable instructions that may cause the controller totransmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna may further cause the controller to: transmit a first signalwhich omits any unique identifiers that uniquely identify anyneighboring passive wireless transponders.

The machine-executable instructions that may cause the controller totransmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna may further cause the controller to: transmit a first signalwhich includes a unique identifier that uniquely identifies the passivewireless transponder.

A method of operation may be summarized as including repeatedlyproviding an interrogation carrier wave to the plurality of passivewireless transponders, the interrogation carrier wave which causes thepassive wireless transponders to transmit to at least one neighboringpassive wireless transponder; receiving information from at least one ofthe plurality of passive wireless transponders, the received informationindicative of whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each interrogation carrier wave; anddetermining whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each interrogation carrier wave. Thepassive wireless transponders may be grouped in pairs, each passivewireless transponder of a respective one of the pairs opposed to oneanother across an edge of a selectively openable passage, and receivinginformation from at least one of the plurality of passive wirelesstransponders, the received information indicative of whether each of thepassive wireless transponders have successfully transmitted to at leastone respective neighboring passive wireless transponder in response toeach interrogation signal includes receiving information form at leastone passive wireless transponder of each pair, the received informationindicative of whether the passive wireless transponders of therespective pair successively communicated with one another. The passivewireless transponders may be grouped in pairs, each passive wirelesstransponder of a respective one of the pairs opposed to one anotheracross an edge of a selectively openable passage, and repeatedlyproviding an interrogation signal to the plurality of passive wirelesstransponders includes providing the interrogation signals which, foreach pair cause at least a first passive wireless transponder of a pairto transmit an addressed signal to a second passive wireless transponderof the pair. The passive wireless transponders may be grouped in pairs,each passive wireless transponder of a respective one of the pairsopposed to one another across an edge of at least one flap, anddetermining whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each interrogation signal includes,for each pair determining whether at least one of the passive wirelesstransponders of the pair has successfully transmitted to the other oneof the passive wireless transponders of the pair in response to eachinterrogation signal. The passive wireless transponders may be groupedin pairs, each passive wireless transponder of a respective one of thepairs opposed to one another across an edge of at least one flap, anddetermining whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each interrogation signal includes,for each pair determining whether at least one of the passive wirelesstransponders of the pair has successfully transmitted to the other oneof the passive wireless transponders of the pair in response to eachinterrogation signal which encodes a defined command. The passivewireless transponders may be grouped in pairs, each passive wirelesstransponder of a respective one of the pairs opposed to one anotheracross an edge of a selectively openable passage, the pairs spaced fromone another such that a nearest neighbor of any one of the passivewireless transponders is the other wireless passive transponder of thepair, and determining whether each of the passive wireless transpondershave successfully transmitted to at least one respective neighboringpassive wireless transponder in response to each interrogation signalincludes, for each pair determining whether at least one of the passivewireless transponders of the pair has successfully transmitted to theother one of the passive wireless transponders of the pair in responseto each interrogation signal. Repeatedly providing an interrogationsignal to the plurality of passive wireless transponders, theinterrogation signal which may cause the passive wireless transpondersto transmit to at least one neighboring passive wireless transponder mayinclude repeatedly providing the interrogation signal from aninterrogator system. Receiving information from at least one of theplurality of passive wireless transponders may include receiving theinformation by the interrogator system and determining whether each ofthe passive wireless transponders have successfully transmitted to atleast one respective neighboring passive wireless transponder inresponse to each interrogation signal includes determining by theinterrogator system whether each of the passive wireless transpondershave successfully transmitted to at least one respective neighboringpassive wireless transponder. Receiving information from at least one ofthe plurality of passive wireless transponders may include receiving theinformation by a host processor-based system from the interrogatorsystem and determining whether each of the passive wireless transpondershave successfully transmitted to at least one respective neighboringpassive wireless transponder in response to each interrogation signalincludes determining by the host processor-based system whether each ofthe passive wireless transponders have successfully transmitted to atleast one respective neighboring passive wireless transponder.

An interrogator system to determine the relative positions of aplurality of passive wireless transponders may be summarized asincluding a transceiver to provide an interrogation carrier wave; aprocessor communicably coupled to the transceiver; and aprocessor-readable nontransitory storage medium including machineexecutable instructions that when executed by the processor, cause theprocessor to: repeatedly transmit an interrogation carrier wave to eachof a plurality of passive wireless transponders that causes each of thepassive wireless transponders to transmit a backscatter signal to atleast one neighboring passive wireless transponder; receive informationfrom at least one of the plurality of passive wireless transponders, theinformation received from the at least one of the plurality of passivewireless transponders indicative of whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to each receivedinterrogation carrier wave; and determine based on the receivedinformation whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each received interrogation carrierwave.

The machine readable instructions that may cause the processor torepeatedly transmit an interrogation carrier wave to each of a pluralityof passive wireless transponders, may further cause the processor to:repeatedly transmit an interrogation carrier wave to grouped pairs ofpassive wireless transponders, each passive wireless transponder of arespective one of the pairs positioned in opposition to one anotheracross an edge of a selectively openable passage; and wherein themachine readable instructions that cause the processor to receiveinformation from at least one of the plurality of passive wirelesstransponders, further cause the at least one processor to: receiveinformation from at least one of the plurality of passive wirelesstransponders, the received information indicative of whether each of thepassive wireless transponders have successfully transmitted to at leastone respective neighboring passive wireless transponder in response toeach interrogation signal includes receiving information form at leastone passive wireless transponder of each pair, the received informationindicative of whether the passive wireless transponders of therespective pair successively communicated with one another.

The machine readable instructions that may cause the processor torepeatedly transmit an interrogation carrier wave to each of a pluralityof passive wireless transponders, may further cause the processor to:repeatedly transmit an interrogation carrier wave to grouped pairs ofpassive wireless transponders, each passive wireless transponder of arespective one of the pairs positioned in opposition to one anotheracross an edge of a selectively openable passage; and wherein themachine readable instructions that cause the processor to determinebased on the received information whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to each receivedinterrogation carrier wave, further cause the at least one processor to:determine for each pair of passive wireless transponders whether atleast one of the passive wireless transponders forming the pair hassuccessfully transmitted to the other one of the passive wirelesstransponders forming the pair in response to each interrogation signalthat includes data indicative of an encoded defined command.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is a schematic diagram illustrating an example system forproviding backscatter communication between each of a number of passivewireless transponders, according to one non-limiting illustratedembodiment.

FIG. 2 is a schematic diagram illustrating an example substrateincluding a number of frangible passive wireless transmitters able tobackscatter communicate with at least one other passive wirelesstransmitter in the presence of an interrogation carrier wave, accordingto one non-limiting illustrated embodiment.

FIG. 3 is a schematic diagram illustrating an example arrangement ofordered items each including a passive wireless transmitter able tobackscatter communicate with at least one neighboring passive wirelesstransmitter in the presence of an interrogation carrier wave, accordingto one non-limiting illustrated embodiment.

FIG. 4 is a schematic diagram illustrating an example arrangement ofordered items each including a passive wireless transmitter able tobackscatter communicate with at least one neighboring passive wirelesstransmitter in the presence of an interrogation carrier wave, accordingto one non-limiting illustrated embodiment.

FIGS. 5A and 5B are schematic diagrams illustrating an examplearrangement of at least one pair of passive wireless transmittersarranged to detect the opening of an enclosure via backscattercommunication in the presence of an interrogation carrier wave,according to one non-limiting illustrated embodiment.

FIG. 6 is a high level logic flow diagram of an illustrative method fordetermining the relative spatial relationship between passive wirelesstransponders, according to one non-limiting illustrated embodiment.

FIG. 7 is a high level logic flow diagram of an illustrative method fordetermining the presence of a nearest neighbor spatial relationshipbetween passive wireless transponders, according to one non-limitingillustrated embodiment.

FIG. 8 is a high level logic flow diagram of an illustrative method fordetermining whether a defined signal has passed sequentially through anumber of neighboring passive wireless transponders, according to onenon-limiting illustrated embodiment.

FIG. 9 is a high level logic flow diagram of an illustrative method forpassing a defined signal sequentially through a number of neighboringpassive wireless transponders, according to one non-limiting illustratedembodiment.

FIG. 10 is a high level logic flow diagram of an illustrative method fordetermining whether neighboring passive wireless transponders aremaintained in a proximate spatial relationship over time, according toone non-limiting illustrated embodiment.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc.Communications systems and protocols that are well known to those ofskill in the communications arts or are readily available in the form ofstandards or similar guidance documents have not been shown or describedin detail to avoid unnecessarily obscuring descriptions of theembodiments. Additionally, time-of-flight, time-of-arrival, ordifferential time-of-arrival based position or location determinationmethods that are well known to those of skill in the communications artshave not been shown or described in detail herein. Additionally,detailed specifications of well known electronic components such aspassive radio frequency identification (“RFID”) transducers, RFIDinterrogators, radio frequency receivers, radio frequency transceivers,processors, nontransitory storage or memory, communication and/orswitching protocols and the like have not been shown or described indetail.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, such as“comprises” and “comprising,” are to be construed in an open, inclusivesense that is as “including, but not limited to.”

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contentclearly dictates otherwise. Reference throughout this specification to“one embodiment” or “an embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment. Thus, the appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this specification are not necessarily all referring to thesame embodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

FIG. 1 shows an illustrative system 100 for providing backscatter waves102 by any number of passive wireless transducers 104 responsive toillumination by an interrogation carrier wave 106. Any number of passivewireless transducers 104 a-104 n (collectively “transducers 104”) areilluminated by the interrogation carrier wave 106 generated by a radiofrequency generator 108 such as a radio frequency identification(“RFID”) interrogator. Each transducer 104 includes at least an antenna,an RF front end, and a communicably coupled control circuit. Eachtransducer 104 may optionally include a nontransitory storage mediacommunicably coupled to the antenna and/or control circuit. Upon receiptof the interrogation carrier wave 106, the RF front end derives powerfrom the interrogation signal or carrier wave to power the transducer.The transducers 104 backscatter a portion of the incident energyreceived via the interrogation carrier wave 106 as backscatter wave 102.The transducer may impose data or information on the backscatter wave.For example, the transducers may impose or encode a unique identifier ofthe transponder on the backscatter wave 102.

For example, upon receiving an interrogation carrier wave 106 generatedby an RF transmitter 108, a first transducer 104 a generates abackscatter wave 102 a receivable by any number of second transducers104 b-104 n and optionally by a receiver 110 disposed in a reader orinterrogator device 112. Similarly, each of the second transducers 104b-104 n also generates a respective backscatter wave 102 b-102 n. Thebackscatter waves 102 a-102 n generated by each of the respectivetransducers 104 a-104 n provides a communicable coupling between thetransducers 104. Information, for example data indicative of a uniquetransducer identifier may thus be exchanged between transducers 104.Using such communications, each transducer 104 is able to detect,identify, or otherwise “learn” those other transducers 104 with which acommunicable coupling is possible (i.e., those “other” transducers thatcan be considered “in the neighborhood” of, or neighboring, therespective transducer).

In some instances, each transducer 104 n backscatters a respectivebackscatter wave 102 n having data or information modulated thereon thatis uniquely indicative of the respective transducer 104 n backscatteringthe backscatter wave 102 n. In at least some instances, a reader orinterrogator 112 may receive the backscatter wave 102 n containing theinformation. In other instances, the backscatter wave 102 n may carry orotherwise include modulated data representative of information,commands, and/or instructions communicated between some or all of thetransducers 104 a-104 n, or between some or all of the transducers 104a-104 n and a receiver 110 in a reader or interrogator 112. In someinstances, the backscatter wave 102 provided by each transducer 104 maybe limited in range or signal strength such that only a nearest neighbortransducer 104 is able to receive the backscatter wave 102. In otherinstances, the backscatter wave 102 provided by each transducer 104 maybe limited in range or signal strength such that only limited number oftransducers (e.g., nearest and “next nearest” neighboring transducers)are able to receive the backscatter wave 102.

The transducers 104 a-104 n can include any type or style of current orfuture developed passive, wireless, radio frequency transducer. At itsmost basic, each transducer 104 includes at least an antenna and acommunicably coupled control circuit arranged or configured such that aportion of an incident interrogation carrier wave 106 within aparticular, defined, radio frequency band causes the transducer 104 togenerate a backscatter wave 102 which is broadcast via the antenna. Asdiscussed above, in some instances, one or more nontransitory storagemedia may be communicably coupled to the control circuit.

Such nontransitory storage media may include volatile and/ornon-volatile nontransitory memory. Such storage media may be read-onlyor read/write capable. Non-limiting examples of such memory include:read only memory (ROM), random access memory (RAM), dynamic randomaccess memory (DRAM), electrically erasable programmable read onlymemory (EEPROM), and flash memory. In some instances, the storage mediastores or otherwise retains data representative of an identifier uniqueto the transducer 104. In at least some instances, the datarepresentative of the identifier unique to the transducer 104 n may bemodulated onto the backscatter wave 102 n by the control circuit.

The control circuit may have the capability to execute one or moremachine executable instruction sets upon energization by a receivedinterrogation carrier wave 106. In some instances, all or a portion ofthe machine executable instruction set may be stored in thenontransitory storage coupled to the control circuit. In otherinstances, all or a portion of the machine executable instruction setmay be encoded or otherwise transported as a signal modulated on theincoming interrogation carrier wave 106. In yet other instances, all ora portion of the machine executable instruction set may be encoded orotherwise transported as a signal modulated on a backscatter wave 102 ngenerated by another transducer 104 n. Where such a received backscatterwave 102 n contains modulated information including one or more commandsor machine executable instruction sets executable by a transducercontrol circuit, the control circuit in the recipient transducer 104 canextract and execute the received instructions.

In addition to backscattering its own wave 102, some or all of thetransducers 104 may also beneficially receive backscatter wavesgenerated by other, neighboring, transducers. Where the receivedbackscatter wave carries modulated information identifying thetransducer 104 n responsible for backscattering the wave, such may beused by the recipient transducer 104 to uniquely identify theneighboring transducer 104 n. Each transducer 104 may use the propertiesor parameters of each received backscatter wave 102 to determine one ormore aspects of the relative spatial relationship between the transducer104 and the other, neighboring, transducer(s) 104 backscattering thereceived waves 102. Such backscatter wave properties or parameters mayinclude, but are not limited to, received signal strength (“RSSI”)and/or time-of-flight (“TOF”). For example, transducer 104 a may receivethree backscatter waves 102 b, 102 c, and 102 d backscatteredrespectively by transducers 104 b, 104 c, and 104 d. Based on thereceived signal strengths of the backscatter waves 102 b, 102 c, and 102d, the transducer 104 a can determine transducer 104 c is physicallyclosest (i.e., highest RSSI), 104 d is physically next closest, and 104b is physically most distant (i.e., lowest RSSI).

In another example, transducer 104 a may backscatter a wave 102 aincluding defined information or data that is received by transducers104 b, 104 c, and 104 d. In turn, each of transducers 104 b-104 dbackscatters a respective wave 102 b, 102 c, and 102 d that includesinformation or data identifiable to transponder 104 a. The backscatterwaves 102 b, 102 c, and 102 d are received by transducer 104 a atdifferent times based on the relative distance between transducer 104 aand each of transducers 104 b, 104 c, and 104 d. Using thetime-of-flight (i.e., the time required for the waves 102 b, 102 c, and102 d backscattered by transducer 104 a to return to transducer 104 a),transducer 104 a determines the relative location and/or distance toeach of the transducers 104 b-104 d.

The transmitter 108 can include any device or system capable ofgenerating an interrogation carrier wave 106 in the radio frequency ormicrowave frequency spectrum. The interrogation carrier wave 106 isgenerated at a frequency and phase sufficient to wirelessly transfer orotherwise impart at least a portion of the energy of the interrogationcarrier wave 106 to one or more transducers 104 via the RF front end ofthe transducer. In at least some instances, the transmitter 108generates only the interrogation carrier wave without modulating orotherwise imposing data in the form of a signal on the interrogationcarrier wave 106. In other instances, the transmitter 108 generates theinterrogation carrier wave 106 with information in the form of a signalmodulated or otherwise imposed on the interrogation carrier wave 106. Atleast a portion of the information (e.g., data, commands, combinationsof data and commands) that is modulated on the interrogation carrierwave 106 is received by the transducers 104.

The receiver 110 can include any device or system capable of receivingsome or all of the waves 102 a-102 n backscattered by the transducers104 a-104 n responsive to the receipt of the interrogation carrier wave106 generated by the transmitter 108. In some instances, the transmitter108 and the receiver 110 may be partially or completely integrated intoa single device, i.e., a transceiver. In some instances, the transmitter108 and receiver 110 may be positioned in a single handheld or portabledevice as exemplified by a handheld RFID interrogator. In otherinstance, the transmitter 108 and receiver 110 may be discretecomponents located in different locations, enclosures, or housings.

The transmitter 108, the receiver 110, or both the transmitter and thereceiver may be communicably coupled to a communications interface (notshown in FIG. 1) that enables communication with a host device 120 viaone or more intervening networks 122 (e.g., local area network,enterprise network, wide area network, world-wide network, theInternet). In at least some instances, an interrogator 112 that includesboth a transmitter 108 and a receiver 110 may be a dedicated devicehaving only limited processing speed or capability. To perform processorintensive computations, the interrogator 112 may communicate some or allof the data received from the transponders 104 a-104 n to the externalhost device 120. Such data may include for example, received dataindicative of the identity of each transponder's “nearest neighbor”transponder or received data indicative of the identity oftransponder(s) located in a particular transponder's “neighborhood.”

The external host device 120 can include any system, devices, orcombination of systems and devices communicably coupled to one or morecommunications interfaces capable of bidirectionally exchanging datawith the interrogator 112. In some instances, external host device 120may be collocated with the interrogator 112. In other instances, theexternal host device 120 may be located remote from the interrogator112. In at least some instances, one or more networks 122 communicablycoupled a single external host device 120 to a plurality ofinterrogators 112. One or more nontransitory storage devices 124 may beincluded in or communicably coupled to the external host device 120. Thenontransitory storage devices 124 may include one or more data stores ordatabases containing transponder identification data such as dataindicative of unique identifiers associated with transponders 104 a-104n.

FIG. 2 shows an illustrative system 200 in which an object or enclosure202 (e.g., a cardboard shipping container or box) is sealed using anadhesive backed substrate 204 containing a number of transducers 104. Inat least some implementations, each of the transducers 104 a-104 nembedded in the substrate may include one or more frangible ordisruptable elements that are positioned upon and/or coupled to thesubstrate 204 in a manner such that any attempt to remove or otherwiseinterrupt the continuity of the substrate 204 results in the physicaland/or electrical destruction of at least one of the transducers 104. Inother instances, the substrate 204 includes individual transducers 104a-104 n positioned in physical locations beyond which one or moretransducers 104 are unable to recognize or identify a “nearestneighbor.” Such positioning may result in the inability for at least onetransducer to identify at least one of its nearest neighbors in responseto any disruption to the continuity of the substrate (e.g., by cuttingor tearing). Such substrates 204 are beneficial in deterring anddetecting unauthorized access to the interior portion and/or contents ofthe enclosure 202.

In a first implementation, an interrogator 112 receives backscatterwaves 102 a-102 n, each provided by a respective transducer 104 a-104 nresponsive to the receipt of an interrogation signal 106. In such animplementation, each of the backscatter waves 102 a-102 n includes dataindicative of the identity of the backscattering transducer. Uponreceipt of the backscattered waves 102 a-102 n, the interrogator 112and/or external host system 120 determines whether the data indicativeof the identities of the transducers 104 a-104 n providing thebackscattered waves 102 a-102 n compare favorably with stored dataindicative of the identities of the transducers 104 a-104 n included inthe substrate 204 attached or otherwise coupled to the particularenclosure 202. In at least some instances, a nontransitory storagemedium communicably coupled to the interrogator 112 or the external hostsystem 120. If the interrogator 112 or the external host system 120determines a mismatch or if a number of transducers 104 exceeding adefined threshold fail to respond, the interrogator 112 at least onehuman-perceptible output capable of alerting a system user of potentialtampering with the enclosure 202 is provided.

In a second implementation, the transducers 104 a-104 n unidirectionallycommunicate via backscatter waves 102 a-102 n data indicative of acommand or similar information to each successive nearest neighbortransducer until the command or signal transits a closed loop pathwayformed by the substrate 204. In at least some instances, the substrate204 extends continuously around a perimeter of the enclosure 202. Insuch instances, the interrogator 112 provides an interrogation carrierwave 106 to a first transducer 104 a. Responsive to the receipt of theinterrogation carrier wave 106, the first transducer 104 a backscattersa wave 102 a that includes instructions or other data that causes atleast the “nearest neighbor” transducer 104 b to backscatter a wave 102b that includes similar instructions or data. Each subsequent transducer104 _(x) in turn, backscatters a one-way, “daisy-chain,” type wave 102_(x) that include instructions or data that cause the next “nearestneighbor” transducer 104 _(x+1) to backscatter a wave 102 _(x+1)containing the instructions or data. Each transponder 104 a-104 nincluded in the substrate 204 thus passes the instructions or data tothe “nearest neighbor” transponder in a manner similar to a “token.” Theprocess is repeated sequentially until the backscatter wave 102 nbackscattered by the “last” transducer 104 n in the substrate isreceived by the first transducer 104 a, or until a damaged or displacedtransducer 104 prevents the backscattering of the wave 102 that includesthe instructions or data to a “nearest neighbor” transponder.

In some instances, upon the return of the instruction, command, or datato the first transponder 104 a, the first transponder 104 a backscattersa wave 102 a receivable by the interrogator 112 that includes datarepresentative of a “SUCCESS” message. On the other hand, upon a failureof the instruction, command, or data to return to the first transducer104 a within a defined time interval, the first transponder 104 abackscatters a wave 102 a receivable by the interrogator 112 thatincludes data representative of a “FAILURE” message. In turn, theinterrogator 112 and/or a communicably coupled external host system 120can provide at least one human-perceptible output capable of alerting asystem user of potential tampering with the enclosure 202.

In a third implementation, the transducers 104 a-104 n communicate viabackscatter waves 102 a-102 n data indicative of instructions or data toeach successive nearest neighbor transducer until the command or datareaches the “end” of the pathway formed by an open-ended (i.e., notforming a closed loop) substrate 204. In at least some instances, thesubstrate 204 extends only partially around a perimeter of the enclosure202. In such instances, the interrogator 112 provides an interrogationcarrier wave 106 to a first transducer 104 a. Responsive to the receiptof the interrogation carrier wave 106, a first transducer 104 a on thesubstrate 204 generates a backscatter wave 102 a that includesinstructions or other data that causes at least the “nearest neighbor”transducer 104 b to backscatter a wave 102 b that includes similarinstructions or data. Each subsequent transducer 104 _(x) in turn,backscatters a one-way, “daisy-chain,” type wave 102 _(x) that includesinstructions causing the next “nearest neighbor” transducer 104 _(x+1)to backscatter a wave 102 _(x+1) that includes the instructions or data.Each transponder 104 a-104 n thus passes the instructions or data to the“nearest neighbor” transponder in a manner similar to a “token.”

The process is repeated sequentially until the defined “last” transducer104 n in the substrate 204 receives the wave 102 backscattered by its“nearest neighbor.” The “last” transponder 104 n then backscatters awave 102 n that includes data representative of the instructions or datain a reverse direction back to the “nearest neighbor” providing theincoming backscatter wave 102 n. Each subsequent transducer 104 _(x) inturn, backscatters a one-way, “daisy-chain,” type wave 102 _(x) thatincludes instructions causing the next “nearest neighbor” transducer 104_(x−1) to backscatter a wave 102 _(x−1) that includes the instructionsor data to a “nearest neighbor” transponder. Each transponder 104 a-104n included in the substrate 204 thus passes on two occasions (i.e., oncein a “forward” direction and once in a “reverse” direction) theinstructions or data to the “nearest neighbor” transponder in a mannersimilar to a “token.” The process is repeated sequentially until thewave 102 b backscattered by the second transducer 104 b in the substrateis received by the first transducer 104 a, or until a damaged ordisplaced transducer 104 prevents the transmission of the backscatterwave 102 containing the instruction or data to a “nearest neighbor”transponder.

In some instances, upon the return of the instruction, command, or datato the first transponder 104 a, the first transponder 104 a backscattersa wave 102 a receivable by the interrogator 112 that includes datarepresentative of a “SUCCESS” message. On the other hand, upon a failureof the instruction, command, or data to return to the first transducer104 a within a defined time interval, the first transponder 104 abackscatters a wave 102 a receivable by the interrogator 112 thatincludes data representative of a “FAILURE” message. In turn, theinterrogator 112 and/or a communicably coupled external host system 120can provide at least one human-perceptible output capable of alerting asystem user of potential tampering with the enclosure 202.

Thus, in some instances any alteration to or disruption of the substrate204 causes the generation by the interrogator 112 and/or external hostsystem 120 of an output indicative of tampering with the enclosure 202.In other instances, any alteration to or disruption of the substrate 204interrupts the one-way or bidirectional transmission of a backscatterwave 102 that includes instructions or data in a “daisy-chain” mannerbetween “nearest neighbors” or proximately positioned passive wirelesstransponders 104. In either event, a failure of a passive wirelesstransponder 104 to respond with a backscatter wave 102 provides theinterrogator 112 with an indication that the substrate 204 includesdamaged or displaced transponders 104 a-104 n that may indicateunauthorized tampering with the enclosure 202.

FIG. 3 shows an illustrative system 300 in which a number of objects 302a-302 n (collectively “objects 302”), each having a respective passivewireless transponder 104 a-104 n physically coupled thereto, arearranged in a defined order and illuminated by an interrogation carrierwave 106 provided by an interrogator 112. Each of the passive wirelesstransponders 104 a-104 n can include a communicably couplednontransitory storage that includes data indicative of a uniqueidentifier associated with the respective transducer 104. Library books,each containing a uniquely identifiable RFID tag that are arranged in adefined order on a library shelf provide but one simple example of suchan arrangement of objects 302.

In a first implementation, an interrogator 112 receives waves 102 a-102n, each backscattered by a respective passive wireless transponder 104a-104 n responsive to the receipt of an interrogation carrier wave 106.In such an implementation, upon receipt of the interrogation carrierwave 106, each of the passive wireless transponders 102 a-102 ndetermines, using backscatter waves 102 the identity of its “nearestneighbor” transponders 104. Thus, as depicted in FIG. 3, transponder 104b would receive backscatter waves 102 a and 102 d and identifytransponders 104 a and 104 d as “nearest neighbors.” Similarly,transponder 104 d would receive backscatter waves 102 b and 102 c andidentify transponders 104 b and 104 c as “nearest neighbors.” Eachpassive wireless transponder would then backscatter a respective wave102 that includes data indicative of the identified “nearest neighbors.”Continuing with the example in FIG. 3, transponder 104 b wouldbackscatter a signal that includes data indicating transponders 104 aand 104 d as “nearest neighbors.” Each of the transponders 104 a-104 nwould backscatter a respective wave 102 a-102 n that includes similar“nearest neighbor” data.

Upon receipt of the backscattered waves 102 a-102 n, the interrogator112 and/or external host system 120 determines whether the “nearestneighbor” data provided by each of the transponders 104 a-104 n comparesfavorably with stored data indicative of the identities of the “nearestneighbor” transponders 104 a-104 n. Responsive to the detection ofdiscrepancies between the “nearest neighbor” data provided by eachtransponder 104 a-104 n and the stored “nearest neighbor” data, theinterrogator 112 and/or the communicably coupled external host system120 generates one or more human-perceptible alerts.

In a second implementation, each of the transponders 104 a-104 nincludes a nontransitory storage containing data indicative of theidentified nearest neighbor transponders. Thus, for example, thenontransitory storage in transponder 104 b will contain data indicativeof the identity of nearest neighbor transponders 104 a and 104 c. Inresponse to a received interrogation carrier wave 106, each transponder104 a-104 n can determine the identity of one or more “nearest neighbor”transponder 104, for example by generating a backscatter wave 102 andmeasuring the received signal strength of backscatter waves102 generatedby other transponders. After determining the identity of one or morenearest neighbor transducers, each transducer 104 a-104 n compares theidentity of the determined nearest neighbor transponder with the storeddata indicative of the identity of nearest neighbor transponders.

Responsive to the detection of discrepancies between the determinednearest neighbor transponder data and the stored nearest neighbortransponder data, a transponder 104 generates a backscatter wave 102that includes data indicative of the discrepancy. For example, iftransponder 104 b detects the identities of determined nearest neighborsdo not include transponders 104 a and 104 c, but instead includetransponders 104 a and 104 d, transponder 104 b can generate abackscatter signal 102 b that includes an error message indicative ofthe discrepancy. In some instances, the error message provided by thetransponder may include additional data indicative of the determinednearest neighbors. Responsive to the receipt of a backscatter wave 102including data indicative of a discrepancy, the interrogator 206generates one or more human-perceptible alerts. If the transponders 104a-104 n provide determined nearest neighbor data to the interrogator206, the interrogator may advantageously identify those objects that areout of order and may also advantageously identify the appropriatelocations of the misplaced objects.

FIG. 4 shows an illustrative system 400 in which a number of objects 402a-402 n, each having a respective transducer 104 a-104 n physicallycoupled thereto, are arranged in a defined two-dimensional order andilluminated by an interrogation carrier wave 106 provided by aninterrogator 206. Each of the transducers 104 a-104 n can include anontransitory storage that includes data indicative of a uniqueidentifier associated with the transducer 104. Shoe boxes, eachcontaining a uniquely identifiable RFID tag that are arranged in adefined two-dimensional matrix on store shelf provide a simple exampleof such an arrangement of tagged objects.

In operation, upon receipt of an interrogation carrier wave 106, each ofthe transponders 104 can respond by firstly generating one or morebackscatter waves 102 to determine the identities of the nearestneighbor transponders, and secondly by communicating a backscatter wave102 including data indicative of the identities of the determinednearest neighbor transponders to the interrogator 206. Upon receivinginformation indicative of the nearest neighbor transponders from some orall of the transponders 104, the interrogator 206 determines therelative spatial relationship between at least some of the objects 402a-402 n based on the returned transponder data. In at least someinstances, the interrogator 206 provides the system user with a humanperceptible output (e.g., a display) of the relative spatialrelationship between the objects 402 based on the received transponderdata. In some instances, the interrogator 206 can advantageously providethe system user with an indication of the location of a defined object,for example the location of a specific shoe box on a wall containing alarge number of physically similar or identical shoe boxes.

In a first implementation, in response to a received interrogationcarrier wave 106, each transponder 104 a-104 n determines the identityof one or more “nearest neighbor” transducers. In such instances, eachtransponder 104 a-104 n generates at least one backscatter wave 102 anddetermines the identity of one or more nearest neighbor transponders,for example using the RSSI or TOF techniques previously discussed. Afterdetermining the identity of the one or more nearest neighbortransducers, each transducer 104 a-104 n generates a backscatter wave102 a-102 n that includes data indicative of the determined nearestneighbor transducers. For example, transducer 402 f will generate abackscatter wave 102 d including data identifying transponders 104 a,104 b, 104 c, 104 e, 104 g, 104 i, 104 j, and 104 k as nearest neighbortransponders. Each transponder 104 a-104 n illuminated by theinterrogation carrier wave 106 will perform a similar determination ofthe identities of the nearest neighbor transponders and will return thenearest neighbor identities to the interrogator 206 as data included ina backscatter wave 102 a-102 n.

The interrogator 206 combines the nearest neighbor identity datareceived from the transponders 104 a-104 n to determine the relativespatial location, position, or configuration of each transponder withrespect to at least a portion of the other transponders. Identifying therelative location, position, or configuration of each transponderadvantageously permits the interrogator to determine the relativespatial location, position or configuration of the object attached toeach transponder. In at least some instances, each of the transponders104 may perform all or a portion of the spatial location, position, orconfiguration determination and communicate such data to theinterrogator 206 via data included in a backscatter wave 106. Theinterrogator 206 may include one or more output devices capable ofproviding the system user with an indication of the location of aparticular transponder and/or object relative to other transponders orobjects. Thus, for example, an interrogator may advantageously permit awarehouse worker to identify a particular item located on a number ofstacked shelves containing a large number of outwardly similar items.

FIGS. 5A and 5B show an illustrative system 500 in which an enclosure502 includes one or more displaceable members 504 a-504 n for accessingan internal volume or space located at least partially within theenclosure 502. Although only one is shown in FIGS. 5A and 5B,transponder pairs 510, each including two transponders 104 a and 104 b,are positioned proximate and across an edge of a void providing accessto the interior of the enclosure. For example, in FIG. 5A, a firsttransponder 104 a is positioned on a removable door 504 and a secondtransponder 104 b is positioned on the enclosure 502 such that thetransponders 104 a and 104 b are proximate when the door 504 is in aCLOSED position and distal when the door 504 is in an OPEN position. Inanother example, in FIG. 5B, a first sensor 104 a is positioned on afirst box flap 504 a and a second sensor 104 b is positioned on a secondbox flax 504 b such that sensors 104 a and 104 b are proximate when thebox flaps are in a CLOSED position and distal when either or both of thebox flaps are in an OPEN position.

FIG. 5A shows an interrogator 206 positioned internal to the enclosure502, FIG. 5B shows an interrogator 206 positioned external to theenclosure 502. Either continuously or periodically, the interrogator 206generates an interrogation carrier wave 106. Upon receiving theinterrogation carrier wave 106, the transponders 104 a, 104 b in eachtransponder pair 510 determine whether they are positioned in a “nearestneighbor” or proximate position indicating the displaceable member(s)504 is in a CLOSED position and the interior of the enclosure 502 isinaccessible. If the transponders 104 a, 104 b are not positioned in a“nearest neighbor” or proximate position, the displaceable member(s) 504are in an OPEN position and the interior of the enclosure 502 isaccessible. Thus, the position of the transponders 104 a, 104 b canprovide an indication of whether the enclosure 502 has been broached andthe interior portion accessed. One or both transponders 104 a, 104 b ineach transponder pair 510 generate a backscatter wave 102 a, 102 bincluding data indicative of the nearest neighbor transponder (if any).The interrogator 206 receives the backscatter signal and generates asignal indicative of whether the transponders are physically disposedproximate (i.e., in a “nearest neighbor” configuration) or distal (i.e.,not in a “nearest neighbor” configuration). The interrogator 206 canstore in a communicably coupled nontransitory storage data indicative ofthe relative spatial relationship (i.e., proximate or distal) of thetransponders 104 in each transponder pair 510 attached to the enclosure502. Storing data indicative of the relative spatial relationship of thetransponders 104 provides a historical record indicative of anoccurrence where the interior of the enclosure 502 was accessible. Insome instances, the interrogator 206 can communicate an alert to one ormore external devices when a distal relative spatial relationshipbetween the transponders 104 in one or more transponder pairs 510 isdetected.

FIG. 6 shows a high level method 600 of determining the relative spatialposition of passive wireless transponders 104. A radio frequencygenerator 108 generates an interrogation carrier wave 106 thatilluminates a number of passive wireless transponders 104 a-104 n.Responsive to the receipt of the interrogation carrier wave 106, each ofthe transponders 104 a-104 n generates a respective backscatter wave 102a-102 n. In turn, each of the transponders 104 a-104 n receives one ormore backscatter waves 102 a-102 n generated by other transponders. Inat least some instances, the transponders 104 a-104 n use one or morereceived backscatter wave properties (e.g., received signal strength or“RSSI”) to determine the relative distance between the transponderoriginating the backscatter wave and the transponder receiving thebackscatter wave. In other instances, each transponder 104 broadcasts abackscatter wave to all or a portion of the remaining transponders andmeasures the time-of-flight of the backscatter signals provided by allor a portion of the remaining transponders to determine the relativedistance between the transponder originating the backscatter wave andthe transponder receiving the backscatter wave. The method 600 ofdetermining the relative spatial position of a number of passivewireless transponders commences at 602.

At 604, an external host device 110 receives from each of a number ofpassive wireless transponders 104 a-104 n a respective backscattersignal 102 a-102 n that includes information indicative of at least oneneighboring passive wireless transponder spatially proximate therespective passive wireless transponder 104 a-104 n from which theinformation is received. Such information may be modulated on, encodedin, or otherwise carried by the backscatter wave 102 generated by therespective transponder 104.

At 606, using the information indicative of the at least one neighboringpassive wireless transponder that is spatially proximate the respectivepassive wireless transponder 104 a-104 n from which the information isreceived, the external host device 110 determines the relative positionof the passive wireless transponders 104. For example, if transponder104 a returns a backscatter wave 102 a that includes data indicativethat transponder 104 c is spatially proximate, transponder 104 c returnsa backscatter wave 102 c that includes data indicative that transponder104 e is spatially proximate, and transponder 104 e returns abackscatter wave 102 e that includes data indicative that transponder104 g is spatially proximate, the external host device 110 can deducethe relative spatial position of the transponders is A-C-E-G. The method600 of determining the relative spatial position of a number of passivewireless transponders concludes at 608.

FIG. 7 shows a high level method 700 of determining by each of a numberof passive wireless transponders the relative spatial position of one ormore other spatially proximate passive wireless transponder(s) 104. Eachof a number of passive wireless transponders 104 a-104 n receives aninterrogation carrier wave 106. Responsive to the receipt of theinterrogation carrier wave 106, each of the transponders 104 a-104 ngenerates a respective backscatter wave 102 a-102 n. Based on one ormore backscatter wave 102 a-102 n properties or parameters, each of thetransponders 104 a-104 n determines which of the other passive wirelesstransponders represent spatially proximate neighboring transponders. Insome instances, received signal strength or “RSSI” is used by thetransponder to determine which of the other transponders is spatiallyproximate. In other instances, the time of flight of a backscatter wavereturned by each of the other transponders is used by the transponder todetermine which of the other transponders is spatially proximate. Themethod 700 of determining by each of a number of passive wirelesstransponders the relative spatial position of one or more otherspatially proximate passive wireless transponder(s) commences at 702.

At 704, each of a number of passive wireless transponders 104 a-104 nreceives an interrogation carrier wave 106 provided by an RF generator108.

In response to receiving the interrogation carrier wave, eachtransponders 104 a-104 n generates a respective backscatter wave 102a-102 n. In at least some instances, the backscatter wave 102 generatedby each transponder 104 may include information such as a uniqueidentifier assigned to the respective transponder 104 generating thebackscatter wave 102. Based on one or more properties or parameters ofeach received backscatter wave 102, each transponder 104 determineswhich of the other passive wireless transponders represent spatiallyproximate neighboring transponders. In some instances, received signalstrength or “RSSI” is used by the transponder to determine which of theother passive wireless transponders is spatially proximate. In otherinstances, the time of flight of a backscatter wave returned by each ofthe other passive wireless transponders is used by the transponder todetermine which of the other passive wireless transponders is spatiallyproximate.

At 706, each of the passive wireless transponders 104 a-104 n generatesa respective backscatter wave 102 a-102 n that includes informationindicative of the identity of one or more other spatially proximatetransponders as determined at 704. The method 700 of determining by eachof a number of passive wireless transponders the relative spatialposition of one or more other spatially proximate passive wirelesstransponder(s) concludes at 708.

FIG. 8 shows a high level method 800 of determining interruptions in aknown sequence of passive wireless transponders based on the sequentialrebroadcast of a backscatter wave from transponder to neighboringtransponder in a defined sequence. A number of passive wirelesstransponders 104 may be physically configured such that neighboringtransponders 104 are arranged in a known or defined order. For example,a number of passive wireless transponders 104 a-104 n may be coupled toa substrate in a known or defined order. In at least some instances, thesubstrate may include a material such as an adhesive backed tape usefulfor sealing packages prior to placing the packages into commerce and thepassive wireless transponders 104 can include frangible passive wirelesstransponders that are rendered inoperable if damaged (e.g., cut through)or if the substrate is forcibly removed from a surface (e.g., torn off apackage). Such an implementation advantageously provides an indicationof tampering with the substrate and/or the item to which the substrateis attached.

In some instances, the substrate 204 may be applied about thecontinuously about a perimeter of a package 202 such that the ends ofthe substrate “meet” or otherwise fall adjacent to each other. In suchinstances, the passive wireless transponders 104 a-104 n disposed in thesubstrate form a “loop” about the package and the backscatter waves 102sequentially communicated by each transponder 104 to a neighboringtransponder 104 will work their way in a single direction around theloop back to the originating or “first” transponder that initiated thesequential transmission of the backscatter wave 102.

In other instances, the substrate 204 may be applied to only a portionof the perimeter of a package and the ends of the substrate do not meetor otherwise fall adjacent to each other. In such instances, the passivewireless transponders 104 a-104 n disposed in the substrate form an openloop and the backscatter waves 102 sequentially communicated by eachtransponder 104 to a neighboring transponder 104 will work their wayfrom the transponder at the first end of the substrate to thetransponder at the second end of the substrate 204. In some instances,the backscatter waves 102 sequentially communicated by each transponder104 to a neighboring transponder 104 will work their way from thetransponder at the first end of the substrate to the transponder at thesecond end of the substrate 204 and back the transponder at the firstend of the substrate 204. The method of determining interruptions in aknown sequence of passive wireless transponders based on the sequentialrebroadcast of a backscatter wave from transponder to neighboringtransponder in a defined sequence commences at 802.

At 804, an interrogation carrier wave 106 is provided to a number ofpassive wireless transponders 104 a-104 n arranged in a defined series,sequence, or configuration. Responsive to the receipt of theinterrogation signal 106, a first passive wireless transponder 104 acommunicates a backscatter wave 102 a to a neighboring transponder 104b, which in turn communicates a backscatter wave 102 b to a neighboringtransponder 104 c, and so on. A damaged or missing transponder 104interrupts the sequential transmission of the backscatter wave 102. Inat least some instances, a respective nontransitory storage mediacommunicably coupled to each transponder 104 can store data indicativeof the source of the received backscatter wave 102.

At 806, at least one of the passive wireless transponders 104 generatesa respective backscatter wave 102 that includes data indicative ofwhether each of the passive wireless transponders have successfullytransmitted to a respective neighboring passive wireless transponder ina defined order. In some implementations, such a backscatter wave 102 iscommunicated to the interrogator by the “first” or originatingtransponder 104. Such a transponder may be positioned at the first endof a substrate attached to a first object in a defined series ofobjects. In such instances, the first transponder 104 can generate thebackscatter signal responsive to receiving from a neighboringtransponder a backscatter wave 102 indicative of a successful sequentialtransmission of the backscatter wave 102 by a defined sequence oftransponders 104 a-104 n.

At 808, using the information included in the backscatter wave 102provided by the first transponder 104, the external host device 110determines whether each of the passive wireless transponders havesuccessfully transmitted to a respective neighboring passive wirelesstransponder in a defined order or sequence. In at least someimplementations, the external host device can generate one or more humanperceptible alarms or annunciations to indicate a failure to transmit inthe defined order or sequence. The method of determining interruptionsin a known sequence of passive wireless transponders based on thesequential rebroadcast of a backscatter wave from transponder toneighboring transponder in a defined sequence concludes at 810. FIG. 9shows a high level method 900 of determining by a passive wirelesstransponder 104 whether the sequential rebroadcast of a backscatter waveby a known sequence or arrangement of transponders has been interrupted.The method of determining by a passive wireless transponder 104 whetherthe sequential rebroadcast of a backscatter wave by a known sequence orarrangement of transponders has been interrupted commences at 902.

At 904, an interrogation carrier wave 106 is received by a first passivewireless transponder 104 a. The first passive wireless transponder 104 ais a member of a plurality of passive wireless transponders 104 a-104 narranged in a defined series, sequence, or configuration.

At 906, responsive to the receipt of the interrogation signal 106, thefirst passive wireless transponder 104 a communicates a backscatter wave102 a to a neighboring transponder 104 b, which in turn communicates abackscatter wave 102 b to a neighboring transponder 104 c, and so on. Adamaged or missing transponder 104 interrupts the sequentialtransmission of the backscatter wave 102.

At 908, the first passive wireless transponder 104 a receives a secondsignal, such as a second backscatter wave 102 generated by a spatiallyproximate or neighboring passive wireless transponder 104. The secondbackscatter wave 102 includes data indicative of whether each of aplurality of passive wireless transponders which includes at least thefirst passive wireless transponder 104 a and at least the spatiallyproximate or neighboring passive wireless transponder 104, havesuccessfully transmitted a backscatter wave 102 to one another in adefined order. The method of determining by a passive wirelesstransponder 104 whether the sequential rebroadcast of a backscatter waveby a known sequence or arrangement of transponders has been interruptedconcludes at 910.

FIG. 10 shows a high level method 1000 of determining the relativepositions of a plurality of passive wireless transponders 104 a-104 n byrepeatedly providing an interrogation carrier wave 106 from a radiofrequency generator 110 to the plurality of passive wirelesstransponders 104 a-104 n. In some implementations, passive wirelesstransponders 104 a-104 n may be positioned at defined locations in, on,or about an enclosure 502. Such positioning may provide an indication ofundesired access to the interior portion of the enclosure. For example,passive wireless transponders 104 a-104 n may be positioned in pairs 510on an exterior or interior surface proximate an opening (e.g., door, boxflaps) providing access to an interior space of an enclosure 502. Uponinterrogation, if both passive wireless transponders in each transponderpair 510 indicate placement proximate the other transponder in thetransponder pair 510, such indicates the integrity of the enclosure 502has not be compromised. On the other hand, should one or both of thepassive wireless transponders in a transponder pair indicate placementdistal from the other transponder in the transponder pair 510, suchindicates a potential compromise of enclosure 502 integrity.

An interrogator 206, positioned internal or external to the enclosure502 may repeatedly provide an interrogation carrier wave 106 to theplurality of passive wireless transponders 104 positioned in, on, orabout the enclosure 502. Data indicative of the relative physicalposition of some or all of the passive wireless transponders (e.g.,proximate, distal) may be stored by the interrogator 206 in acommunicably coupled nontransitory storage. Date and time dataindicative of the date and time the relative physical position of someor all of the passive wireless transponders was obtained may also bestored in the nontransitory storage. Such advantageously provides ahistory of the relative position of some or all of the plurality ofpassive wireless transponders. In some instances, the interrogator 206can transmit one or more signals that include data indicative of therelative physical position of some or all of the passive wirelesstransponders to one or more remote devices via a communicably coupledcommunications interface. The method 1000 of determining the relativepositions of a plurality of passive wireless transponders 104 a-104 n byrepeatedly providing an interrogation carrier wave 106 from a radiofrequency generator 110 to the plurality of passive wirelesstransponders 104 a-104 n commences at 1002.

At 1004, an interrogator 206 positioned internal or external to theenclosure 502 repeatedly provides at least an interrogation carrier waveto some or all of a plurality of passive wireless transponders 104 a-104n positioned in, on, or about an enclosure 502. In at least someinstances, at least a portion of the transponders104 a-104 n may bepositioned in pairs with each transponder 104 in the pair disposed onopposing surfaces of a movable member 504 a-504 b providing access to aninterior portion of the enclosure 502. Such positioning permitsdetection of movement of movable member 504 a-504 b which may indicatean attempt to access the interior portion of the enclosure 502. Theinterrogator may provide such interrogation carrier waves 106 on aperiodic, intermittent, or continuous basis.

At 1006, responsive to the receipt of the interrogation carrier wave 106by some or all of the plurality of passive wireless transponders 104a-104 n, each of the passive wireless transponders 104 generates abackscatter signal 102 to determine the identity of another physicallyproximate nearest neighbor transponder. If the moveable members 504 a,504 b are proximate each other, the identity of the physically proximatenearest neighbor transponder is the other transponder in the pair 510.Some or all of the plurality of passive wireless transponders generateat least one backscatter wave 102 containing information indicative ofthe identity of the other passive wireless transponder determined to bephysically proximate the respective transponder 104 (if any).

At 1008, the interrogator 206 determines whether each of the pluralityof passive wireless transponders have successfully transmitted to atleast one neighboring passive wireless transponder in response to eachinterrogation carrier wave 102 received by the plurality of passivewireless transducers 104 a-104 n. In some instances, the interrogator206 determines whether each of the plurality of passive wirelesstransponders 104 a-104 n have successfully transmitted to at least oneneighboring passive wireless transponder.

In other instances, each of the plurality of transponders 104 a-104 ncompares data indicative of the neighboring passive wireless transponderstored in a communicably coupled nontransitory storage with the dataindicative of the determined neighboring passive wireless transponder.In such instances, some or all of the passive wireless transponders 104a-104 n may communicate information indicative of the comparison results(i.e., MATCH or NO MATCH) to the interrogator 206 via a backscatter wave102 generated by the respective transducer. The method 1000 ofdetermining the relative positions of a plurality of passive wirelesstransponders 104 a-104 n by repeatedly providing an interrogationcarrier wave 106 from a radio frequency generator 110 to the pluralityof passive wireless transponders 104 a-104 n concludes at 1010.

Also for example, the various methods may include additional acts, omitsome acts, and may perform the acts in a different order than set out inthe various flow diagrams. The use of ordinals such as first, second andthird, do not necessarily imply a ranked sense of order, but rather mayonly distinguish between multiple instances of an act or structure.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet are incorporated herein by reference, in their entirety. Aspectsof the embodiments can be modified, if necessary, to employ systems,circuits and concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A method to determine the relative positions of a number of passivewireless transponders, the method comprising: receiving information fromeach of a plurality of passive wireless transponders, the informationreceived from each of the passive wireless transponders identifying atleast one neighboring passive wireless transponder that is spatiallyproximate the respective passive wireless transponder from which theinformation is received; and determining a relative position of thepassive wireless transponders with respect to one another based at leastin part on the information received from the passive wirelesstransponders.
 2. The method of claim 1 wherein receiving informationincludes receiving information by an interrogator system, and furthercomprising: providing an interrogation carrier wave to the plurality ofpassive wireless transponders which causes at least some of theplurality of passive wireless devices to communicate with one another.3. The method of claim 2 wherein determining a relative position of thepassive wireless transponders with respect to one another based at leastin part on the information received from the passive wirelesstransponders includes determining the relative position of the passivewireless transponders with respect to one another by a hostprocessor-based system, the host processor-based system remotely locatedwith respect to the interrogator system.
 4. The method of claim 2wherein determining a relative position of the passive wirelesstransponders with respect to one another based at least in part on theinformation received from the passive wireless transponders includesdetermining the relative position of the passive wireless transponderswith respect to one another by the interrogator system.
 5. The method ofclaim 2 wherein determining a relative position of the passive wirelesstransponders with respect to one another based at least in part on theinformation received from the passive wireless transponders includesdetermining the relative position of the passive wireless transponderswith respect to one another by at least one of the passive wirelesstransponders.
 6. The method of claim 2 wherein providing aninterrogation carrier wave includes: providing by the interrogatorsystem an interrogation carrier wave having a signal including datamodulated thereon.
 7. The method of claim 6 wherein providing by theinterrogator system an interrogation carrier wave having a signalincluding data modulated thereon includes: providing by the interrogatorsystem an interrogation carrier wave having a signal modulated thereon,the signal including data representative of at least one command.
 8. Themethod of claim 1 wherein the plurality of wireless transponders arelocated about an enclosure, and further comprising: determining based onthe received information whether tampering with the enclosure hasoccurred; and causing an indication of tampering to be provided inresponse to a determination that tampering with the enclosure hasoccurred.
 9. The method of claim 1 wherein the plurality of wirelesstransponders are located about packaging, and further comprising:determining based on the received information whether tampering with thepackaging has occurred; and causing an indication of tampering to beprovided in response to a determination that that tampering with thepackaging has occurred.
 10. The method of claim 1 wherein the pluralityof wireless transponders are located across at least one flap of apackaging, and further comprising: determining based on the receivedinformation whether tampering with the packaging has occurred; andcausing an indication of tampering to be provided in response to adetermination that that tampering with the packaging has occurred. 11.The method of claim 1, further comprising: determining if any of thepassive wireless transponders are out of order with respect to in adefined array.
 12. The method of claim 1 wherein determining a relativeposition of the passive wireless transponders with respect to oneanother based at least in part on the information received from thepassive wireless transponders includes generating a virtual map of theplurality of passive wireless transponders, the virtual map whichrepresents relative spatial positions of the passive wirelesstransponders with respect to one another.
 13. An interrogator system todetermine the relative positions of a plurality of passive wirelesstransponders, the interrogator system comprising: a transceiver toprovide an interrogation carrier wave; a processor communicably coupledto the transceiver; and a processor-readable nontransitory storagemedium including machine executable instructions that when executed bythe processor, cause the processor to: receive information from each ofa plurality of passive wireless transponders that identifies at leastone neighboring passive wireless transponder that is spatially proximatethe respective passive wireless transponder from which the informationis received; and determine a relative position of the passive wirelesstransponders with respect to one another based at least in part on theinformation received from the passive wireless transponders.
 14. Thesystem of claim 13 wherein the machine executable instructions thatcause the processor to receive information from each of a plurality ofpassive wireless transponders further cause the processor to: receiveinformation from each of a plurality of passive wireless transponderslocated about an enclosure; determine based on the received informationwhether tampering with the enclosure has occurred; and responsive to adetermination that tampering with the enclosure has occurred, generate ahuman perceptible output indicative that tampering with the enclosurehas occurred.
 15. The system of claim 13 wherein the machine executableinstructions that cause the processor to receive information from eachof a plurality of passive wireless transponders further cause theprocessor to: receive information from each of a plurality of passivewireless transponders located about an package; determine based on thereceived information whether tampering with the package has occurred;and responsive to a determination that tampering with the package hasoccurred, generate a human perceptible output indicative that tamperingwith the package has occurred.
 16. The system of claim 13 wherein themachine executable instructions that cause the processor to receiveinformation from each of a plurality of passive wireless transpondersfurther cause the processor to: receive information from each of aplurality of passive wireless transponders located across at least onepackaging flap; determine based on the received information whethertampering with the package has occurred; and responsive to adetermination that tampering with the package has occurred, generate ahuman perceptible output indicative that tampering with the package hasoccurred.
 17. The system of claim 13 wherein the machine executableinstructions further cause the processor to: compare informationreceived information from each of a plurality of passive wirelesstransponders with stored data indicative of a defined array; anddetermine whether any of the passive wireless transponders are out oforder with respect to the defined array.
 18. The system of claim 13wherein the machine executable instructions further cause the processorto: generate a virtual map of the plurality of passive wirelesstransponders, the virtual map representative of the relative spatialpositions of the passive wireless transponders with respect to eachother.
 19. A method of operation of a passive wireless transponder, themethod comprising: in response to receipt of an interrogation carrierwave, receiving information from each of a number of other passivewireless transponders by the passive wireless transponder; andtransmitting information identifying at least one of the other passivewireless transponders as a neighboring passive wireless transponder thatis spatially proximate the passive wireless transponder from which theinformation is received.
 20. The method of claim 19, further comprising:categorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder.
 21. The method of claim 20wherein categorizing at least one of the other passive wirelesstransponders as a neighboring passive wireless transponder includescategorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder based at least in part on asignal strength of a signal received by the passive wireless transponderfrom one of the other passive wireless transponders.
 22. The method ofclaim 20 wherein categorizing at least one of the other passive wirelesstransponders as a neighboring passive wireless transponder includescategorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder based at least in part on asignal strength of a signal received by the passive wireless transponderfrom one of the other passive wireless transponders relative to a signalstrength of a signal received by the passive wireless transponder fromother ones of the other passive wireless transponders.
 23. The method ofclaim 20 wherein categorizing at least one of the other passive wirelesstransponders as a neighboring passive wireless transponder includescategorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder based at least in part on atime-of-flight of a signal received by the passive wireless transponderfrom one of the other passive wireless transponders.
 24. The method ofclaim 20 wherein categorizing at least one of the other passive wirelesstransponders as a neighboring passive wireless transponder includescategorizing at least one of the other passive wireless transponders asa neighboring passive wireless transponder based at least in part on atime-of-flight of a signal received by the passive wireless transponderfrom one of the other passive wireless transponders relative to atime-of-flight of a signal received by the passive wireless transponderfrom other ones of the other passive wireless transponders.
 25. Themethod of claim 20 wherein transmitting information identifying at leastone of the other passive wireless transponders as a neighboring passivewireless transponder includes backscattering an interrogation carrierwave received from an interrogator system with the information encodedin the backscattered signal.
 26. A passive wireless transponder,comprising: an antenna; a controller communicably coupled to theantenna; and a nontransitory storage media communicably coupled to thecontroller including machine-executable instructions that cause thecontroller to: receive information from each of a number of otherpassive wireless transponders responsive to the receipt of aninterrogation carrier wave by the antenna; and transmit information thatidentifies at least one of the other passive wireless transponders as aspatially proximate, neighboring, passive wireless transponder.
 27. Thetransponder of claim 26 wherein the machine-executable instructions thatcause the controller to transmit information that identifies at leastone of the other passive wireless transponders as a spatially proximate,neighboring, passive wireless transponder further cause the controllerto: identify at least one of the other passive wireless transponders asa spatially proximate, neighboring, passive wireless transponder basedon a received signal strength representative of a signal received fromeach of the other passive wireless transponders; and transmitinformation that identifies at least one of the other passive wirelesstransponders as a spatially proximate, neighboring, passive wirelesstransponder.
 28. The transponder of claim 26 wherein themachine-executable instructions that cause the controller to transmitinformation that identifies at least one of the other passive wirelesstransponders as a spatially proximate, neighboring, passive wirelesstransponder further cause the controller to: compare a signal strengthrepresentative of a signal received from one of the other passivewireless transponders with signal strengths of signals received fromother ones of the other passive wireless transponders; identify at leastone of the other passive wireless transponders as a spatially proximate,neighboring, passive wireless transponder based on the compared signalstrengths; and transmit information that identifies at least one of theother passive wireless transponders as a spatially proximate,neighboring, passive wireless transponder.
 29. The transponder of claim26 wherein the machine-executable instructions that cause the controllerto transmit information that identifies at least one of the otherpassive wireless transponders as a spatially proximate, neighboring,passive wireless transponder further cause the controller to: identifyat least one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder based on atime-of-flight parameter of a signal received from each of the otherpassive wireless transponders; and transmit information that identifiesat least one of the other passive wireless transponders as a spatiallyproximate, neighboring, passive wireless transponder.
 30. Thetransponder of claim 26 wherein the machine-executable instructions thatcause the controller to transmit information that identifies at leastone of the other passive wireless transponders as a spatially proximate,neighboring, passive wireless transponder further cause the controllerto: compare a time-of-flight parameter of a signal received from one ofthe other passive wireless transponders with time-of-flight parametersof signals received from other ones of the other passive wirelesstransponders; identify at least one of the other passive wirelesstransponders as a spatially proximate, neighboring, passive wirelesstransponder based on the compared times-of-flight; and transmitinformation that identifies at least one of the other passive wirelesstransponders as a spatially proximate, neighboring, passive wirelesstransponder.
 31. A method of operation, the method comprising: providingan interrogation carrier wave to the plurality of passive wirelesstransponders, the interrogation carrier wave which causes the passivewireless transponders to transmit to a neighboring passive wirelesstransponder in a defined order; receiving information from at least oneof the plurality of passive wireless transponders, the informationreceived from the at least one of the plurality of passive wirelesstransponders indicative of whether each of the passive wirelesstransponders have successfully transmitted to a respective neighboringpassive wireless transponder in the defined order; and determining basedon the received information whether each of the passive wirelesstransponders have successfully transmitted to a respective neighboringpassive wireless transponder in the defined order.
 32. The method ofclaim 31 wherein providing an interrogation carrier wave to theplurality of passive wireless transponders includes providing aninterrogation carrier wave which causes the passive wirelesstransponders to successively pass a command along a defined sequence ofthe passive wireless transponders.
 33. The method of claim 31 whereinproviding an interrogation carrier wave to the plurality of passivewireless transponders includes providing an interrogation carrier wavewhich causes the passive wireless transponders to successively pass acommand along a defined sequence of the passive wireless transponders ina closed loop starting from and ending with a first one of the passivewireless transponders.
 34. The method of claim 31 wherein providing aninterrogation carrier wave to the plurality of passive wirelesstransponders includes providing an interrogation carrier wave whichcauses the passive wireless transponders to successively pass a commandalong a defined sequence of the passive wireless transponders in a firstdirection from a first one to a last one of the passive wirelesstransponders in the defined sequence.
 35. The method of claim 31 whereinproviding an interrogation carrier wave to the plurality of passivewireless transponders includes providing an interrogation carrier wavesignal which causes the passive wireless transponders to successivelypass a command along a defined sequence of the passive wirelesstransponders in a first direction from a first one to a last one of thepassive wireless transponders in a first defined sequence and then in asecond direction from the last one to the first one of the passivewireless transponders in a second defined sequence.
 36. The method ofclaim 31 wherein providing an interrogation carrier wave to theplurality of passive wireless transponders includes providing aninterrogation carrier wave which causes the passive wirelesstransponders to successively pass information along a defined sequenceof the passive wireless transponders.
 37. The method of claim 31 whereinproviding an interrogation carrier wave to the plurality of passivewireless transponders includes providing an interrogation carrier wavewhich causes the passive wireless transponders to successively passinformation along a defined sequence of the passive wirelesstransponders in a closed loop starting from and ending with a first oneof the passive transponders.
 38. The method of claim 31 whereinproviding an interrogation carrier wave to the plurality of passivewireless transponders includes providing an interrogation carrier wavewhich causes the passive wireless transponders to successively passinformation along a defined sequence of the passive wirelesstransponders in a first direction from a first one to a last one of thepassive wireless transponders in the defined sequence.
 39. The method ofclaim 31 wherein providing an interrogation carrier wave to theplurality of passive wireless transponders includes providing aninterrogation carrier wave which causes the passive wirelesstransponders to successively pass information along a defined sequenceof the passive wireless transponders in a first direction from a firstone to a last one of the passive wireless transponders in a firstdefined sequence and then in a second direction from the last one to thefirst one of the passive wireless transponders in a second definedsequence.
 40. The method of claim 31 wherein the interrogation carrierwave causes the passive wireless transponders to each retrieve from amemory of the passive wireless transponder a unique identifier for atleast one respective neighboring passive wireless transponder.
 41. Themethod of claim 31 wherein the plurality of wireless transponders arelocated about an enclosure, and further comprising: determining based onthe received information whether tampering with the enclosure hasoccurred; and causing an indication of tampering to be provided inresponse to a determination that tampering with the enclosure hasoccurred.
 42. The method of claim 40 wherein the plurality of wirelesstransponders are located about packaging, and further comprising:determining based on the received information whether tampering with thepackaging has occurred; and causing an indication of tampering to beprovided in response to a determination that tampering with thepackaging has occurred.
 43. The method of claim 31 wherein the pluralityof wireless transponders are located across at least one flap of apackaging, and further comprising: determining based on the receivedinformation whether tampering with the packaging has occurred; andcausing an indication of tampering to be provided in response to adetermination that tampering with the packaging has occurred.
 44. Aninterrogator system to determine the relative positions of a pluralityof passive wireless transponders, the interrogator system comprising: atransceiver to provide an interrogation carrier wave; a processorcommunicably coupled to the transceiver; and a processor-readablenontransitory storage medium including machine executable instructionsthat when executed by the processor, cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto transmit a backscatter signal to a neighboring passive wirelesstransponder in a defined order; receive information from at least one ofthe plurality of passive wireless transponders, the information receivedfrom the at least one of the plurality of passive wireless transpondersindicative of whether each of the passive wireless transponders havesuccessfully transmitted to a respective neighboring passive wirelesstransponder in the defined order; and determine based on the receivedinformation whether each of the passive wireless transponders havesuccessfully transmitted to a respective neighboring passive wirelesstransponder in the defined order.
 45. The system of claim 44 wherein themachine-executable instructions that cause the processor to transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders further cause the processor to: transmit an interrogationcarrier wave to each of a plurality of passive wireless transpondersthat causes each of the plurality of wireless transponders tosuccessively transmit a command using a backscatter signal to a definedsequence of passive wireless transponders.
 46. The system of claim 44wherein the machine-executable instructions that cause the processor totransmit an interrogation carrier wave to each of a plurality of passivewireless transponders further cause the processor to: transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders that causes each of the plurality of wireless transpondersto successively transmit a command using a backscatter signal to adefined sequence of passive wireless transponders in a closed loop,starting and ending with a first one of the passive wirelesstransponders.
 47. The system of claim 44 wherein the machine-executableinstructions that cause the processor to transmit an interrogationcarrier wave to each of a plurality of passive wireless transpondersfurther cause the processor to: transmit an interrogation carrier waveto each of a plurality of passive wireless transponders that causes eachof the plurality of wireless transponders to successively transmit acommand using a backscatter signal to a defined sequence of passivewireless transponders in a first direction from a first one to a lastone of the passive wireless transponders in a defined sequence.
 48. Thesystem of claim 44 wherein the machine-executable instructions thatcause the processor to transmit an interrogation carrier wave to each ofa plurality of passive wireless transponders further cause the processorto: transmit an interrogation carrier wave to each of a plurality ofpassive wireless transponders that causes each of the plurality ofwireless transponders to successively transmit a command using abackscatter signal to a defined sequence of passive wirelesstransponders in a first direction from a first one to a last one of thepassive wireless transponders in a first defined sequence and then in asecond direction from the last one to the first one of the passivewireless transponders in a second defined sequence.
 49. The system ofclaim 44 wherein the machine executable instructions that cause theprocessor to receive information from each of a plurality of passivewireless transponders further cause the processor to: receiveinformation from each of a plurality of passive wireless transponderslocated about an enclosure; determine based on the received informationwhether tampering with the enclosure has occurred; and responsive to adetermination that tampering with the enclosure has occurred, generate ahuman perceptible output indicative that tampering with the enclosurehas occurred.
 50. The system of claim 44 wherein the machine executableinstructions that cause the processor to receive information from eachof a plurality of passive wireless transponders further cause theprocessor to: receive information from each of a plurality of passivewireless transponders located across at least one packaging flap;determine based on the received information whether tampering with thepackage has occurred; and responsive to a determination that tamperingwith the package has occurred, generate a human perceptible outputindicative that tampering with the package has occurred.
 51. A method ofoperation of a first passive wireless transponder, the methodcomprising: receiving an interrogation carrier wave by the first passivewireless transponder; in response to receipt of the interrogationcarrier wave, transmitting a first signal by the first passive wirelesstransponder to at least one neighboring passive wireless transponder;and receiving a second signal from at least one neighboring passivewireless transponder by the first passive wireless transponder, thereceived second signal indicative of whether each of a plurality ofpassive wireless transponders, which includes at least the first and atleast the neighboring passive wireless transponders, have successfullytransmitted to one another in a defined order.
 52. The method of claim51, further comprising: determining whether each of the passive wirelesstransponders have successfully transmitted to a respective neighboringpassive wireless transponder in the defined order based on the receivedsecond signal.
 53. The method of claim 51, further comprising:determining by at least one circuit of the first passive wirelesstransponder whether each of the passive wireless transponders havesuccessfully transmitted to a respective neighboring passive wirelesstransponder in the defined order based at least in part on the receivedsecond signal.
 54. The method of claim 51, further comprising:transmitting information to an interrogation system by the first passivewireless transponder, the information indicative of whether each of theplurality of passive wireless transponders have successfully transmittedto one another in a defined order.
 55. The method of claim 51 whereintransmitting a first signal by the first passive wireless transponderincludes transmitting a first signal which includes at least one uniqueidentifier that uniquely identifies a respective neighboring passivewireless transponder.
 56. The method of claim 51 wherein transmitting afirst signal by the first passive wireless transponder includestransmitting a first signal which omits any unique identifiers thatuniquely identify any neighboring passive wireless transponders.
 57. Themethod of claim 51 wherein transmitting a first signal by the firstpassive wireless transponder includes transmitting a first signal whichincludes a unique identifier that uniquely identifies the first passivewireless transponder.
 58. A passive wireless transponder, comprising: anantenna; a controller communicably coupled to the antenna; and anontransitory storage media communicably coupled to the controllerincluding machine-executable instructions that cause the controller to:transmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna; and receive a second signal from at least one neighboringpassive wireless transponder, the received second signal indicative ofwhether each of a plurality of passive wireless transponders havesuccessfully transmitted a defined signal to one another in a definedorder.
 59. The transponder of claim 58 wherein the machine-executableinstructions further cause the controller to: determine whether each ofthe passive wireless transponders have successfully transmitted to arespective neighboring passive wireless transponder in the defined orderbased on the received second signal.
 60. The transponder of claim 58wherein the machine-executable instructions further cause the controllerto: transmit a signal to an interrogation system, the signal includingindicative of whether each of the plurality of passive wirelesstransponders have successfully transmitted to one another in a definedorder.
 61. The transponder of claim 58 wherein the machine-executableinstructions that cause the controller to transmit a first signal to atleast one neighboring passive wireless transponder responsive to receiptof an interrogation carrier wave by the antenna further cause thecontroller to: transmit a first signal which includes at least oneunique identifier that uniquely identifies a respective neighboringpassive wireless transponder.
 62. The transponder of claim 58 whereinthe machine-executable instructions that cause the controller totransmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna further cause the controller to: transmit a first signalwhich omits any unique identifiers that uniquely identify anyneighboring passive wireless transponders.
 63. The transponder of claim58 wherein the machine-executable instructions that cause the controllerto transmit a first signal to at least one neighboring passive wirelesstransponder responsive to receipt of an interrogation carrier wave bythe antenna further cause the controller to: transmit a first signalwhich includes a unique identifier that uniquely identifies the passivewireless transponder.
 64. A method of operation, the method comprising:repeatedly providing an interrogation carrier wave to the plurality ofpassive wireless transponders, the interrogation carrier wave whichcauses the passive wireless transponders to transmit to at least oneneighboring passive wireless transponder; receiving information from atleast one of the plurality of passive wireless transponders, thereceived information indicative of whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to eachinterrogation carrier wave; and determining whether each of the passivewireless transponders have successfully transmitted to at least onerespective neighboring passive wireless transponder in response to eachinterrogation carrier wave.
 65. The method of claim 64 wherein thepassive wireless transponders are grouped in pairs, each passivewireless transponder of a respective one of the pairs opposed to oneanother across an edge of a selectively openable passage, and receivinginformation from at least one of the plurality of passive wirelesstransponders, the received information indicative of whether each of thepassive wireless transponders have successfully transmitted to at leastone respective neighboring passive wireless transponder in response toeach interrogation signal includes receiving information form at leastone passive wireless transponder of each pair, the received informationindicative of whether the passive wireless transponders of therespective pair successively communicated with one another.
 66. Themethod of claim 64 wherein the passive wireless transponders are groupedin pairs, each passive wireless transponder of a respective one of thepairs opposed to one another across an edge of a selectively openablepassage, and repeatedly providing an interrogation signal to theplurality of passive wireless transponders includes providing theinterrogation signals which, for each pair cause at least a firstpassive wireless transponder of a pair to transmit an addressed signalto a second passive wireless transponder of the pair.
 67. The method ofclaim 64 wherein the passive wireless transponders are grouped in pairs,each passive wireless transponder of a respective one of the pairsopposed to one another across an edge of at least one flap, anddetermining whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each interrogation signal includes,for each pair determining whether at least one of the passive wirelesstransponders of the pair has successfully transmitted to the other oneof the passive wireless transponders of the pair in response to eachinterrogation signal.
 68. The method of claim 64 wherein the passivewireless transponders are grouped in pairs, each passive wirelesstransponder of a respective one of the pairs opposed to one anotheracross an edge of at least one flap, and determining whether each of thepassive wireless transponders have successfully transmitted to at leastone respective neighboring passive wireless transponder in response toeach interrogation signal includes, for each pair determining whether atleast one of the passive wireless transponders of the pair hassuccessfully transmitted to the other one of the passive wirelesstransponders of the pair in response to each interrogation signal whichencodes a defined command.
 69. The method of claim 64 wherein thepassive wireless transponders are grouped in pairs, each passivewireless transponder of a respective one of the pairs opposed to oneanother across an edge of a selectively openable passage, the pairsspaced from one another such that a nearest neighbor of any one of thepassive wireless transponders is the other wireless passive transponderof the pair, and determining whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to eachinterrogation signal includes, for each pair determining whether atleast one of the passive wireless transponders of the pair hassuccessfully transmitted to the other one of the passive wirelesstransponders of the pair in response to each interrogation signal. 70.The method of claim 64 wherein repeatedly providing an interrogationsignal to the plurality of passive wireless transponders, theinterrogation signal which causes the passive wireless transponders totransmit to at least one neighboring passive wireless transponderincludes repeatedly providing the interrogation signal from aninterrogator system.
 71. The method of claim 64 wherein receivinginformation from at least one of the plurality of passive wirelesstransponders includes receiving the information by the interrogatorsystem and determining whether each of the passive wireless transpondershave successfully transmitted to at least one respective neighboringpassive wireless transponder in response to each interrogation signalincludes determining by the interrogator system whether each of thepassive wireless transponders have successfully transmitted to at leastone respective neighboring passive wireless transponder.
 72. The methodof claim 71 wherein receiving information from at least one of theplurality of passive wireless transponders includes receiving theinformation by a host processor-based system from the interrogatorsystem and determining whether each of the passive wireless transpondershave successfully transmitted to at least one respective neighboringpassive wireless transponder in response to each interrogation signalincludes determining by the host processor-based system whether each ofthe passive wireless transponders have successfully transmitted to atleast one respective neighboring passive wireless transponder.
 73. Aninterrogator system to determine the relative positions of a pluralityof passive wireless transponders, the interrogator system comprising: atransceiver to provide an interrogation carrier wave; a processorcommunicably coupled to the transceiver; and a processor-readablenontransitory storage medium including machine executable instructionsthat when executed by the processor, cause the processor to: repeatedlytransmit an interrogation carrier wave to each of a plurality of passivewireless transponders that causes each of the passive wirelesstransponders to transmit a backscatter signal to at least oneneighboring passive wireless transponder; receive information from atleast one of the plurality of passive wireless transponders, theinformation received from the at least one of the plurality of passivewireless transponders indicative of whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to each receivedinterrogation carrier wave; and determine based on the receivedinformation whether each of the passive wireless transponders havesuccessfully transmitted to at least one respective neighboring passivewireless transponder in response to each received interrogation carrierwave.
 74. The system of claim 73 wherein the machine readableinstructions that cause the processor to repeatedly transmit aninterrogation carrier wave to each of a plurality of passive wirelesstransponders, further cause the processor to: repeatedly transmit aninterrogation carrier wave to grouped pairs of passive wirelesstransponders, each passive wireless transponder of a respective one ofthe pairs positioned in opposition to one another across an edge of aselectively openable passage; and wherein the machine readableinstructions that cause the processor to receive information from atleast one of the plurality of passive wireless transponders, furthercause the at least one processor to: receive information from at leastone of the plurality of passive wireless transponders, the receivedinformation indicative of whether each of the passive wirelesstransponders have successfully transmitted to at least one respectiveneighboring passive wireless transponder in response to eachinterrogation signal includes receiving information form at least onepassive wireless transponder of each pair, the received informationindicative of whether the passive wireless transponders of therespective pair successively communicated with one another.
 75. Thesystem of claim 73 wherein the machine readable instructions that causethe processor to repeatedly transmit an interrogation carrier wave toeach of a plurality of passive wireless transponders, further cause theprocessor to: repeatedly transmit an interrogation carrier wave togrouped pairs of passive wireless transponders, each passive wirelesstransponder of a respective one of the pairs positioned in opposition toone another across an edge of a selectively openable passage; andwherein the machine readable instructions that cause the processor todetermine based on the received information whether each of the passivewireless transponders have successfully transmitted to at least onerespective neighboring passive wireless transponder in response to eachreceived interrogation carrier wave, further cause the at least oneprocessor to: determine for each pair of passive wireless transponderswhether at least one of the passive wireless transponders forming thepair has successfully transmitted to the other one of the passivewireless transponders forming the pair in response to each interrogationsignal that includes data indicative of an encoded defined command.